Although large scale integration (LSI) devices LSIs are becoming increasingly faster, it is considered that there is a limit to the transmission capacity of an electrical line that connects between those LSIs or the like. As a technique to break through the limit, expectations are placed on an optical interconnection technique. The optical interconnection technique is a technique that uses an optical line instead of an electrical line used hitherto. Specifically, a configuration is being researched and developed that converts an electrical signal output from an LSI to an optical signal, transmits the signal over a desired distance by using an optical line such as an optical waveguide or an optical fiber and converts the optical signal to an electrical signal to thereby reach an input pin of a destination LSI.
A large number of, as many as 100 or more, input/output electrical terminals are attached to a high-performance LSI, and in the case of applying the optical interconnection technique, it is necessary to replace all electrical signals corresponding to that number of terminals with optical signals. Further, because a high-speed signal of about 10 Gbps undergoes a large loss in electrical line transmission, it is desirable to make conversion into an optical signal in the circumstances where a loss is as small as possible. In other words, an electrical line distance should be shorter. In order to convert the electrical signals corresponding to the large number of input/output electrical terminals to optical signals in the state where a loss in the electrical lines is small, it is important to place an optical module for opto-electric conversion in close proximity to the LSI.
In terms of heating, a heating value increases as the operating speed becomes higher in the above-described high-performance LSI and optical module. With the increase in heating value, the size of a cooling fin or the like for cooling becomes larger. It is desirable that a cooling structure is of like size to the size of the LSI or the optical module.
In the invention disclosed in Patent Document 1, an LSI package with an interface module using a socket is described. For example, in Patent Document 1, a cross-sectional view of an LSI package with an optical interface module is shown in FIG. 10. Note that FIG. 10 in Patent Document 1 is described as FIG. 12 in this specification.
In FIG. 12, a signal processing LSI 1 and an optical interface module 2 are in contact with a heatsink 3. Although the description regarding FIG. 10 in Patent Document 1 refers simply to the heatsink, the detail of the heatsink is described as follows in the paragraph of the specification.
Specifically, it is described in the paragraph that “Further, as the frequency of a signal becomes higher, power consumption per terminal generally tends to increase. For example, in a CPU used for a personal computer or the like, there is an LSI that consumes as much as 70 to 80 W. In light of this, a structure is employed in which a heat spreader and a big heatsink are mounted on the signal processing LSI to enlarge a heat dissipation area and forced air cooling is performed by a fan or the like. On the other hand, as described earlier, because it is necessary to minimize the line length between the signal processing LSI and the interface module, mounting a heatsink for the signal processing LSI causes a lack of extra space for another head sink for the interface module”. It is assumed from this description that air cooling is supposed for the above-described heatsink.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2009-59883